Coiled tubing (CT) (also referred to as endless tubing or continuous tubing) is frequently used for down hole well completions, operations, servicing, etc.
Coiled tubing is typically manufactured from flat plate which is formed into a tubular, longitudinally (or otherwise) welded, heat treated, pressure tested, and rolled into a coil. Heat treating may include annealing.
Some down hole operations benefit from being able to convey electrical power from surface to the bottom hole assembly (BHA) or to communicate signals from surface to the BHA or from the BHA to surface. Wireline is frequently used for these electrical power (may also be referred to as electric line) or communication signals. Examples include directional control or measurement tools, pressure/temperature and other sensors, packers etc.
Wireline can be loosely inserted into finished coiled tubing, for example, by uncoiling the coiled tubing and then pumping a steel cable through the coiled tubing using a cup and then using the steel cable to pull (fish) the wireline through the coiled tubing and recoiling the coiled tubing, by uncoiling the coiled tubing into a well bore and using gravity to drop the wireline into the CT (U.S. Pat. No. 6,148,925 to Moore), or by pumping the wireline into the coiled tubing with the coiled tubing on the reel (U.S. Pat. No. 5,699,996 and U.S. Pat. No. 5,429,194).
Wireline can instead be inserted into coiled tubing during the manufacturing process, for example, by using a spring guide to position the electrical conductor to the side opposite the welding operation and providing cooling to reduce the heat damage to the electrical conductor (U.S. Pat. No. 5,122,209 to Moore et al.), or by using a cable placement tube which conducts coolant along the electrical conductor to prevent heat degradation (the cable placement tube extending past the welding operation and the subsequent heat treating operation) (U.S. Pat. No. 5,121,872 to Legget).
The unrestrained wireline in coiled tubing has a number of problems, including, when the coiled tubing with wireline combination is roiled onto a reel or unrolled from the reel, the difference in radius of the unrestrained wireline results in slack and length problems, during operations, fluid flow past the unrestrained wireline results in slack problems, birdcaging, and in deviated or horizontal wells, the difference in radius results in slack and length problems.
It is, therefore, desirable to provide coiled tubing with wireline secured within.